removal of phosphate from the aqueous environment using iron oxide/activated carbon composites: activated carbon derived from ziziphus nuts as a new precursor

Ziziphus nuts are abundant in khuzestan province, iran, and are considered as an unwanted natural biomass waste. the present study is aimed to develop low-cost activated carbon from ziziphus nuts as a new precursor for the removal of phosphate from the water environment.the iron oxide modification was performed to simultaneously facilitate the adsorbent separation via a simple magnetic process and increase the phosphate removal capacity. the iron oxide/activated carbon composite (ioac) was characterized using xrd, edx, sem, and bet methods. the specific surface area for ioac reached 569.41 m2/g, comparable to that of the commercial activated carbon. while other similar derived-from-biomasses activated carbon reached the phosphate removal capacity of around 15 mg/g, ioac demonstrated the excellent phosphate removal performance of as high as 27 mg/g. also, ioac showed fast adsorption kinetics, achieving equilibrium in only 60 minutes. according to the results, the pseudo-second-order kinetic model was more consistent with the data related to the phosphate adsorption onto the adsorbent than the pseudo-first-order model. the adsorption results using langmuir, freundlich, and webber-morris diffusion models were interpreting. the maximum langmuir adsorption capacity was calculated to be 27 mg/l. the adsorbent was removed from the aqueous solution via a simple magnetic process.